Help with modeling/slicing

I'm hoping for some ideas on how to get my model to work out nicely.

I'm building a case for a project that has four screws to hole the lid to the base. The base has a hex inset for the m3 nut, that transitions to a 3mm hole for the screw shaft. i would like to have the transition from hex to circle be done such that the first layer of the circle is solid, so that it will bridge over the hex hole nicely. When done I'll run a 3mm drill down the hole to clean it out.

I've tried a couple settings in slic3r to create supporting structures, but it fills the entire hex area with fill. I don't really want that. Is there a way to do this in slic3r or should I just add the 0.2mm layer in the model?

Hopefully this description makes sense, and I would think that others have solved this issue before.

thanks,
david

If I understand what you're doing, the the hex nut inset gets filled with support material because there's a round hole at the "roof" of the inset. I would close the roof of the hex nut inset with maybe 1 or 2 mm layer, and then put the circular hole above it for the rest of the required height. You can then just extend the hole down through the roof of the hex nut inset with a drill.

I bought a couple bags of 100 pieces of #6 thread rolling screws and they hang on to plastic tightly without easily stripping. If you use that type of screw you can eliminate the nuts and screw the box together from the bottom without any fasteners showing on the top side. I used to use regular 6-32 screws, but they tended to strip the plastic pretty easily.

Edited 1 time(s). Last edit at 12/10/2015 08:02PM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Yes you understand it correctly. I'll just add a small disc to the top of each hex inset as I can't find a way to get automatic supports created without filling up every hole.

I like those screws as well.

thanks
david

Quote
dpeart
I'll just add a small disc to the top of each hex inset as I can't find a way to get automatic supports created without filling up every hole.

This is what I do. Generally I make the "membrane" 0.25mm high and it works out OK - that way it's just a single bridging layer.

If I am creating my own part in openscad, this is easy to do.

If someone gives me an STL to print and it needs such a membrane, I usually import it into openscad and union it with a 0.25mm high cylinder or cube. Because I don't have the math behind the original part, I will "walk" the membrane into position and then render and export the union as a new STL file.